bip54: clarify sigops counting, borrow bip16 language

[instagibbs]

The main issue is the text seemed ambiguous on whether the limit applied per input, or over the total transaction summing over all inputs.

I added some language directly ripped from bip16, and made it clearer, I hope, that each field is evaluated separately.

[instagibbs]

cc @darosior

[darosior]

Thanks, i agree the language could be clearer and your change improves it.

[darosior]

Suggested change

	1. OP_CHECKSIG and OP_CHECKSIGVERIFY count as 1 signature operation, whether or not they are evaluated.
	1. `CHECKSIG` and `CHECKSIGVERIFY` count as 1 signature operation, whether or not they are evaluated.

(Here and below)

In the rest of the document opcodes are referred to without the "OP_" prefix and are preformatted.

[instagibbs]

done, but left OP_1/OP_16 for clarity

[darosior]

Suggested change

	2. OP_CHECKMULTISIG and OP_CHECKMULTISIGVERIFY immediately preceded by OP_1 through OP_16 are counted as 1 to 16 signature operation, whether or not they are evaluated.
	2. OP_CHECKMULTISIG and OP_CHECKMULTISIGVERIFY immediately preceded by OP_1 through OP_16 are counted as 1 to 16 signature operations, whether or not they are evaluated.

Or maybe?

Suggested change

	2. OP_CHECKMULTISIG and OP_CHECKMULTISIGVERIFY immediately preceded by OP_1 through OP_16 are counted as 1 to 16 signature operation, whether or not they are evaluated.
	2. OP_CHECKMULTISIG and OP_CHECKMULTISIGVERIFY immediately preceded by OP_1 through OP_16 are counted as 1 to 16 signature operation(s), whether or not they are evaluated.

[instagibbs]

first suggestion taken

[darosior]

Could you put this sentence directly before the sentence "The accounting is the same as for ..." instead of in a new paragraph by itself?

It would read:

It applies to all transactions in the block except the coinbase transaction. For each input in the transaction, count the number of CHECKSIG and CHECKMULTISIG in the input scriptSig and previous output's scriptPubKey, including the P2SH redeemScript. If the total summed over all transaction inputs is strictly higher than 2500, the transaction is invalid. The accounting is the same as for bip-0016, evaluating the scriptSig, scriptPubKey, and P2SH redeemScript separately:

1. OP_CHECKSIG and OP_CHECKSIGVERIFY count as 1 signature operation, whether or not they are evaluated.
2. OP_CHECKMULTISIG and OP_CHECKMULTISIGVERIFY immediately preceded by OP_1 through OP_16 are counted as 1 to 16 signature operation, whether or not they are evaluated.
3. All other OP_CHECKMULTISIG and OP_CHECKMULTISIGVERIFY are counted as 20 signature operations, whether or not they are evaluated.

Which i find preferable.

[instagibbs]

done